the monday after thanksgiving weekend when all businesses are open and people start buying from these businesses and shipping their purchases from black friday and the weekend for family and friends. The beginning of the busy season for the shipping industry.

after the four day thanksgiving weekend I sent out all the shit I bought after thanksgiving to the relatives on black monday.

The first Monday after the 4th of July weekend. Called this because by this time people have to start going back to work so there's no more fireworks being lit off, so the smoke clears and everything is seemingly "blacker."

guy waking up:AHMAHGAD what happened to the side of the house!
wife:oh honey it's just black monday
guy waking up:oh ok, where's breakfast?